Climate Change and the Oceans

气候变化与海洋

• 批准号: NE/D00876X/1
• 负责人: Gavin Foster
• 金额: $ 59.08万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FD00876X%2F1
• 关键词: Climate; Change; Oceans

The research I propose concerns two fundamental feedback processes within the Earth's climate system / the concentration of atmospheric CO2 and the circulation strength of the oceans. Feedback processes amplify any external forcing of the climate caused by, for example, variations in the Earth's orbit around the sun. Both processes play important roles in the modern climate system, yet their roles in the past, and in particular, their predicted roles in future climate change are uncertain. It is the principal aim of this proposal to reduce this uncertainty by reconstructing the behaviour of these two systems at key times in the past. The first part of the proposed research concerns the concentration of carbon dioxide in the atmosphere. CO2 is an important greenhouse gas such that variations in the amount of atmospheric CO2 are thought to have an important control on the Earth's climate. Indeed, over the last 2.5 million years the climate of the Earth has oscillated between periods of extreme cold (called glacial periods) and comparable warmth (interglacial periods like today). Importantly, these swings in climate have been accompanied by changes in the concentration of atmospheric CO2 (pCO2). The overall driving force for the waxing and waning of ice sheets are subtle variations in the orbit of the Earth around the sun, which influence the amount and seasonal distribution of solar radiation received at high latitudes. Variations in the concentrations of CO2 probably globalise and enhance this orbital forcing. The exact mechanisms responsible for altering pCO2 are not known but probably involve the oceans (the largest store of carbon on the planet that can respond with sufficient rapidity). In order to examine this role, I propose to generate a record of past ocean acidity (pH) in a variety of sensitive areas of the ocean using the boron isotopic composition of planktic and benthic foraminifera (calcareous single celled protists that are common throughout the ocean and are preserved in deep sea sediments). Since the acidity of the ocean largely determines pCO2, I will be able, from this record, to identify how CO2 is stored and released from the deep sea during the waxing and waning of the ice sheets and potentially isolate its role in causing the transitions from one climate state to another. The second part of this proposal concerns the circulation of the oceans. The Equator, which receives more heat from the sun, is hotter than the poles, and it is this temperature gradient that drives ocean (and atmospheric) circulation. The Atlantic portion of ocean circulation is a particularly important and sensitive part of the circulation system. Here, the Gulf Stream carries warm, salty water from the low latitudes to the North Atlantic. These waters then cool, lose heat to the atmosphere and become dense (salty cold water is denser than fresh warm water) and, as a result, sink. They then flow southward at depth, forming the return arm of the convection cell. The release of heat by this mode of circulation is not only important in ameliorating the climate of maritime Europe, but it can influence the overall climate of the planet by determining the water temperature in the Artic seas, where sea-ice forms. Sea-ice is highly reflective and more sea-ice results in more of the Sun's energy being reflected back into space, and hence can influence global temperature. The role of this circulation pattern in future climate scenarios is uncertain; one way to reduce this uncertainty is to examine ocean circulation in the geological past. I propose to use a new analytical technique, involving the laser microsampling of ferromanganese crusts (metallic encrustations that precipitate very slowly from seawater at depth) to reconstruct the strengths and patterns of circulation in the past when the climate was significantly colder (during glacial periods) and warmer than today (the Mid-Pliocene).

我提出的研究涉及地球气候系统内的两个基本反馈过程/大气二氧化碳浓度和海洋环流强度。反馈过程会放大由地球绕太阳轨道变化等引起的气候外部强迫。这两个过程在现代气候系统中都发挥着重要作用，但它们在过去的作用，特别是它们在未来气候变化中的预测作用是不确定的。该提案的主要目的是通过重建这两个系统在过去关键时刻的行为来减少这种不确定性。拟议研究的第一部分涉及大气中二氧化碳的浓度。二氧化碳是一种重要的温室气体，大气中二氧化碳含量的变化被认为对地球气候具有重要的控制作用。事实上，在过去 250 万年里，地球气候在极冷时期（称为冰期）和相当温暖的时期（如今天的间冰期）之间波动。重要的是，这些气候波动伴随着大气二氧化碳浓度 (pCO2) 的变化。冰盖增减的总体驱动力是地球绕太阳轨道的微妙变化，这影响了高纬度地区接收到的太阳辐射的数量和季节分布。二氧化碳浓度的变化可能会全球化并增强这种轨道强迫。改变 pCO2 的确切机制尚不清楚，但可能涉及海洋（地球上最大的碳储存库，可以足够快地做出反应）。为了检验这一作用，我建议使用浮游生物和底栖有孔虫（整个海洋中常见的钙质单细胞原生生物）的硼同位素组成，生成海洋各个敏感区域过去海洋酸度 (pH) 的记录。并保存在深海沉积物中）。由于海洋的酸度在很大程度上决定了pCO2，我将能够从这一记录中确定二氧化碳在冰盖盛衰期间如何从深海储存和释放，并可能分离出其在导致冰盖转变过程中的作用。一种气候状态到另一种气候状态。该提案的第二部分涉及海洋环流。赤道从太阳接收的热量更多，比两极更热，正是这种温度梯度驱动了海洋（和大气）环流。海洋环流的大西洋部分是环流系统中特别重要和敏感​​的部分。在这里，墨西哥湾流将温暖的咸水从低纬度地区输送到北大西洋。然后这些水冷却，向大气散失热量并变得稠密（含盐的冷水比新鲜的温水稠密），结果下沉。然后它们向南深处流动，形成对流单元的返回臂。这种循环方式释放的热量不仅对于改善欧洲海洋气候很重要，而且还可以通过确定海冰形成的北冰洋的水温来影响地球的整体气候。海冰具有高度反射性，更多的海冰会导致更多的太阳能量被反射回太空，从而影响全球温度。这种环流模式在未来气候情景中的作用是不确定的；减少这种不确定性的一种方法是研究过去地质时期的海洋环流。我建议使用一种新的分析技术，包括对铁锰结壳（从海水深处缓慢沉淀的金属结壳）进行激光微采样，以重建过去气候明显寒冷时（冰川时期）的环流强度和模式比今天（上新世中期）温暖。

项目成果

A core top assessment of proxies for the ocean carbonate system in surface-dwelling foraminifers

对表层有孔虫海洋碳酸盐系统代理的核心顶部评估

• DOI: http://dx.10.1029/2006pa001337
• 发表时间: 2007
• 期刊: Paleoceanography
• 作者: Ni Y

Palaeogeographic controls on climate and proxy interpretation

古地理对气候的控制和代理解释

• DOI: 10.5194/cp-12-1181-2016
• 发表时间: 2015-12-14
• 期刊: Climate of The Past
• 作者: D. Lunt;A. Farnsworth;C. Loptson;G. Foster;P. Markwick;C. O’Brien;R. Pancost;S. Robinson;Neil Wrobel
• 通讯作者: Neil Wrobel

A new boron isotope-pH calibration for Orbulina universa, with implications for understanding and accounting for 'vital effects'

Orbulina universa 的新硼同位素-pH 校准对理解和解释“重要效应”具有重要意义

• DOI: http://dx.10.1016/j.epsl.2016.09.024
• 发表时间: 2016
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Henehan M

Seawater pH, pCO2 and [CO2-3] variations in the Caribbean Sea over the last 130 kyr: A boron isotope and B/Ca study of planktic foraminifera

过去 130 kyr 加勒比海海水 pH、pCO2 和 [CO2-3] 变化：浮游有孔虫的硼同位素和 B/Ca 研究

• DOI: http://dx.10.1016/j.epsl.2008.04.015
• 发表时间: 2008
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Foster G